HOUSTON, TX - AUGUST 25: Eric O'Flaherty #39 of the Oakland Athletics throws in the ninth inning against the Houston Astros at Minute Maid Park on August 25, 2014 in Houston, Texas. (Photo by Bob Levey/Getty Images)

Photo: Bob Levey, Getty Images

HOUSTON, TX - AUGUST 25: Eric O'Flaherty #39 of the Oakland...

Image 4 of 5

Oakland Athletics' Josh Donaldson swings for a two-run double against the Houston Astros in the ninth inning of a baseball game Monday, Aug. 25, 2014, in Houston. (AP Photo/Pat Sullivan)

Photo: Pat Sullivan, Associated Press

Oakland Athletics' Josh Donaldson swings for a two-run double...

Image 5 of 5

HOUSTON, TX - AUGUST 25: Coco Crisp #4 of the Oakland Athletics, left, high fives Eric Sogard #28 afte the final out against the Houston Astros at Minute Maid Park on August 25, 2014 in Houston, Texas. (Photo by Bob Levey/Getty Images)

All was better Monday. Samardzija had one of his best starts for Oakland, not allowing a run until the eighth inning, and Donaldson, back in the lineup after missing a game, had three hits, including two doubles, and drove in three runs in the A's 8-2 victory over Houston.

"I told him there's no chance he's not starting the day I pitch," Samardzija said of Donaldson, adding, "I'll give him a massage on his knee if I have to to get him in there. ... You can't say enough good things about Josh."

Said Donaldson: "I try to lay it on the line for those guys every day no matter how I'm feeling."

Josh Reddick hit a two-run homer in the fourth, his 10th homer of the season and his third in 16 lifetime at-bats off Astros starter Scott Feldman, as Oakland's win, coupled with the Angels' loss, moved the teams back into a tie atop the AL West.

The A's scored five runs in the ninth. Tony Sipp walked the first four batters of the inning, including Coco Crisp to force in a run, and Donaldson knocked a two-run double down the third-base line off Jose Veras. Derek Norris added a two-run single with two outs.

Samardzija had allowed seven hits, two walks and seven runs in 3 2/3 innings his last time out, against the Mets at the Coliseum. Monday, the Astros didn't get a man past second base through the first seven innings, and Samardzija struck out four in a row in the late going before Jose Altuve's two-out single in the eighth and Chris Carter's 31st homer of the season, an opposite-field shot on an 0-2 pitch.

"It didn't even sound like he hit it good," Melvin said. "It wasn't a bad pitch. That was the surprise. I thought he was going to cruise through the eighth and then the decision was whether to let him go back for the ninth because he's the kind of guy who doesn't care about pitch counts if he's got a shutout."

Samardzija said he worked with pitching coach Curt Young on keeping his hands closer to his body at the start of his delivery, and worked on his split-finger fastball. "Those two things combined got me back in the zone," he said. "I took that last one pretty personally and wanted to come out and get back into my groove."

Donaldson said he tweaked his left knee in his final at-bat Saturday. When he planted his foot and drove forward, it gave. He was concerned about the knee's stability, so he had an MRI exam Sunday that showed no structural damage.

Donaldson realized after grounding out in the first that his knee pain is manageable, and ran well on his first double. Then he stole second base after a fifth-inning single, belly flopping into the base and then chuckling about it with Astros second baseman Altuve, a fellow All-Star.

Asked to rate his slide, Donaldson said, "Probably about a zero. That was pretty bad."

Donaldson said the hamstring strain that has bothered him the past several weeks has mostly healed.

Sam Fuld was available in an emergency, but Melvin said he'd like to stay away from him if possible. Fuld banged his left knee Sunday and has some discomfort.

Brandon Moss said before Monday's game that he believes he has discovered the reason for his month-long funk. He realized that on the finish of his swing, not only wasn't he putting any weight on his back foot - he also was picking it up entirely. "Like a bowler," he said. "There was no lower body involved at all. All torque. All hands. I was a mess."